BURKERT 355785 (Type 3320) is an electromotive 2/2-way angle seat shut-off valve designed for demanding process automation environments. Driven by a brushless 24 V DC motor coupled to a precision ball screw linear mechanism, the size AG2 actuator generates a 1300 N linear driving force, displacing the valve swivel plate at speeds up to 6 mm/s. The unit features an internal G 1/2 threaded port (DIN ISO 228-1), a DN15 seat orifice, and a rated water flow coefficient (Kv) of 5.4 m³/h. Configured with a factory delivery status of normally closed (NC) through the integrated SAFEPOS energy-pack module, the valve reliably closes the flow path upon power loss without relying on external pneumatic pressure.

Technical Data of Article 355785

Parameter	Value
Type	3320
Article Number	355785
Circuit Function	2/2-way on/off shut-off valve
Port Connection	G 1/2 internal thread (DIN ISO 228-1)
Orifice / Nominal Seat Size	DN 15 (15 mm / 9/16")
Operating Pressure Range	0 to 25 bar(g)
Nominal Pressure Rating	PN 25 (DIN EN 1333), Class 150 (DIN EN 1759)
Flow Direction	Below seat (against closing direction)
Flow Rate (Kv Water)	5.4 m³/h (Cv 6.2 gpm)
Typical Closing Time	2.2 s (2200 ms)
Travel Speed	6 mm/s
Supply Voltage	24 V DC ± 10 % (maximum residual ripple 10 %)
Operating Current	Max. 3 A (including 1 A charging current for SAFEPOS energy-pack; +2 A at min. temperature)
Standby Power Consumption	2 to 4 W
Duty Cycle	100 % continuous
Fail-Safe Safety Position	Normally closed (NC), via SAFEPOS energy-pack
Seat Seal Material	PTFE (Polytetrafluoroethylene)
Valve Body Material	Stainless steel CF3M
Actuator Size	AG2 (1300 N driving force)
Operating Medium Temperature	-10 °C to +130 °C
Permissible Ambient Temperature	-25 °C to +65 °C (without external modules)
Ingress Protection Rating	IP65 / IP67 (DIN EN 60529), NEMA 4X
Protection Class	III (DIN EN 61140)
Weight	Up to 5.5 kg (AG2 actuator assembly)

Actuator Design and Mechanical Construction

The Type 3320 AG2 linear drive consists of a brushless DC motor, reduction gear, and threaded spindle mechanism that transfers force to the valve stem and closure plate. The system maintains tight shut-off even at the maximum operating pressure of 25 bar(g) in a de-energized holding state.

• Manual Override Options: The actuator features an electrical manual mode operated via pushbuttons beneath the blind cover, as well as a mechanical manual override accessible under the blind cover using a 4 mm Allen key.
• Position Indication: A yellow mechanical indicator stem shows the actual valve position through a transparent window even when power is off. A 360° illuminated LED light ring indicates operating modes, end positions, and diagnostic states.
• SAFEPOS Energy-Pack: The internal electrical energy storage unit charges fully within 120 seconds and powers the valve to its programmed safety position (normally closed) if the 24 V DC main supply fails. The pack is continuously monitored for service life (rated up to 10 years).

Materials of Construction

Wetted metal components are constructed from investment-cast stainless steel CF3M and precision wrought 316/316L alloys. The spindle packing utilizes self-adjusting PTFE V-rings preloaded with a spring assembly. All wetted materials meet European Regulation (EC) 1935/2004 requirements according to the manufacturer declaration.

Item No.	Component	Material
Actuator AG2
1	Blind cover / gateway housing	PPS (standard), stainless steel 1.4301 (ATEX/IECEx)
2	Actuator cover	PPS
3	Static seal	EPDM
4	Actuator housing	Powder-coated aluminium
6	Seal	EPDM
7	Actuator base	PPS
Valve Body & Trim
1	Spindle (stem)	Stainless steel 1.4401 (316) / 1.4404 (316L)
2	Spindle packing seal	PTFE V-seals (filled) with spring compensation
3	Spindle guide bushing	PEEK or stainless steel 1.4404 (316L)
4	Packing gland tube	Stainless steel 1.4401 (316)
5	Body gasket	Graphite or PTFE
6	Swivel plate	Stainless steel 1.4401 (316) / 1.4404 (316L)
7	Valve seat seal washer	PTFE sealing washer
8	Valve body	Stainless steel CF3M

Dimensional Specifications

Connection DN	Thread D	Thread Depth E [mm]	Body Center Height CM [mm]	Face-to-Face LM [mm]	Hex Wrench Flat SW [mm]	Total Height H1 (AG2 Standard) [mm]
DN 15	G 1/2	14	24	65	27	311
DN 20	G 3/4	16	27	75	34	319
DN 25	G 1	18	29.5	90	41	321
DN 32	G 1 1/4	16	36	110	50	330
DN 40	G 1 1/2	18	35	120	55	333
DN 50	G 2	24	45	150	70	367

INFO

Height dimension H1 is given without sealing lift: the actuator rises by approximately 2 mm when seated in the closed position.

Electrical Control and Wiring Interface

Article 355785 utilizes cable feed-through terminals for standard binary switching control. Actuation commands follow standard digital input levels (0 to 5 V = low / log "0"; 10 to 30 V = high / log "1"). Two digital outputs provide feedback signals with individual 100 mA current limits.

• Service Interface: büS service interface accessible under the dummy cover allows communication with a PC or mobile device via Bürkert Communicator software.
• Local Buttons: Two internal buttons beneath the dummy cover permit manual open/close commands and initiation of the X.TUNE stroke adjustment function.

Service, Maintenance, and Replacement Procedures

Available Spare Part Sets for Type 3320

• Swivel plate set: Consists of graphite seal (item 1), swivel plate (item 2), and dowel pin (item 3).
• Packing gland seal set: Consists of packing gland V-rings and seals (item 4), graphite seal, and lubricant.
• Spindle guide for packing gland: Consists of spindle guide (item 5), graphite seal, and lubricant.
• SAFEPOS energy-pack: Replaceable plug-in energy storage module (order code 285834 for AG2).

Removing the Actuator from the Valve Body

Pressure Hazard

Before performing any disassembly, relieve fluid pressure and vent or drain all connected pipelines. Never remove an actuator from a pressurized valve.

Valve Position during Removal

The valve must be driven to the fully open position before unscrewing the actuator from the valve body. Attempting to disassemble the unit while closed damages the seat seal and swivel plate.

1. Electrical Opening: Remove the blind cover by turning it 90° counter-clockwise. Set DIP switch 4 to ON (MANUAL mode). Press and hold the OPEN button until the yellow mechanical position indicator confirms full lift. Disconnect power.
2. Mechanical Opening (De-energized): If 24 V DC power is unavailable, rotate the dummy cover 90° counter-clockwise and remove it. Insert a 4 mm Allen key into the central manual override socket. Apply gentle axial pressure to engage the clutch and rotate counter-clockwise until the indicator confirms the open position. Tightening torque must not exceed 2 Nm.

3. Unscrewing the Body: Clamp the valve body in a holding fixture. Apply an open-end wrench across the body connection flats and unscrew the actuator from the valve body. Never use a pipe wrench.

Swivel Plate Replacement

1. Support the cylindrical hub of the swivel plate in a prism block.
2. Drive out the dowel pin using a 3 mm pin punch (for DN15, spindle diameter 10 mm).
3. Slide the worn swivel plate off the spindle.
4. Mount the new swivel plate onto the spindle, aligning the through-holes.
5. Support the swivel plate on the prism, insert the new dowel pin, and tap it in until centered relative to the spindle axis.

Installing the Actuator and Tightening Torques

• Replace the graphite body gasket before reassembly.
• Ensure the valve actuator remains in the OPEN position during mounting.
• Coat the external threads of the body connection with Klüber paste UH1 96-402.
• Screw the actuator into the valve body using an open-end wrench and tighten to the specified torque:

Connection Size DN	Tightening Torque [Nm]
DN 15	45 ± 3
DN 20	50 ± 3
DN 25	60 ± 3
DN 32	65 ± 3
DN 40	65 ± 3
DN 50	70 ± 3
DN 65	100 ± 3

Packing Gland Replacement (DN15 Connection)

For DN15 (connection size 10/15) units, packing gland maintenance is performed by uncoupling the actuator base:

1. Clamp the body connection in a fixture and remove the 4 screws securing the actuator base to the housing.
2. Separate the actuator housing from the base.
3. Unscrew the spindle guide from the base tube.
4. Using a suitable tool, carefully extract the worn packing gland components without marring the inner guide bore.
5. Lubricate the new packing rings with supplied grease and insert them into the tube in the prescribed stacking sequence.
6. Lubricate spindle guide threads with Klüber paste UH1 96-402 and tighten the guide to 6 Nm (for spindle diameter 10 mm).
7. Reattach the actuator base to the housing, tightening the 4 screws crosswise to 5 Nm.

Replacing the SAFEPOS Energy-Pack

Electrical Discharge

Switch off main power and allow the SAFEPOS energy storage pack to discharge completely before opening the housing. Wait until the LED light ring turns completely off.

1. Rotate the dummy cover 90° counter-clockwise and remove.
2. Remove the two 3 mm hexagon socket screws holding the LED and storage module, then lift out the module.
3. Loosen the 4 captive T25 Torx screws on the actuator cover and remove the cover.
4. Loosen the T10 Torx locking screw on the energy-pack retaining bracket.
5. Grip the bracket and pull the depleted SAFEPOS energy-pack straight out along the guide tracks.
6. Slide the replacement energy-pack (part no. 285834) along the guide tracks until fully seated.
7. Tighten the T10 locking screw, reinstall covers, and reconnect the 24 V DC power supply.

X.TUNE Stroke Calibration

Zero-Pressure Requirement

Never execute the X.TUNE function while the valve is under process pressure. An incorrect calibration under medium load will lead to improper seat seating and uncontrolled valve movement.

Under normal conditions, re-running X.TUNE is not required after factory shipment unless the valve body or seat has been altered. To execute manual calibration: ensure the line is depressurized, remove the dummy cover, and simultaneously depress the OPEN and CLOSE buttons for 5 seconds. Rapid LED flashing confirms calibration progress; steady illumination signals completion.